In general, a heat exchanger is provided with a passage through which a heat exchange medium such as coolant or refrigerant can flow, and performs a heat exchange with the outside air while the heat exchange medium flows through the passage.
For example, the refrigerant compressed by a compressor and thus having a raised temperature is moved to a condenser. The temperature of the refrigerant is lowered by a heat exchange while the refrigerant passes through the condenser and is further lowered while the refrigerant passes through an expansion valve. After that, the refrigerant at the lowered temperature is moved to an evaporator.
In the evaporator, the heat exchange is performed to generate cool air. The cool air is then supplied to a room. In this case, a cooling operation is performed.
Meanwhile, coolant which has cooled a heated engine is moved to a heater core to perform a heat exchange. Warm air is generated by the heat exchange and then supplied to a room. In this case, a heating operation is performed.
A general heat exchanger is shown in FIGS. 1 and 2. A plurality of tubes 130 provided with a flow path 131 for a heat exchange medium therein are coupled with radiating fins 140 and each end portion of the tube 130 is inserted into and coupled to tube inserting holes 121 of a header 120. The header 120 is coupled with a tank 110.
At this time, the tube 130 and the header 120, and the header 120 and the tank 110 are respectively coupled by brazing.
The brazing is a joining method in which a filler material having a melting temperature of more than 450° C. is located at a joint portion of a base metal to be joined and heated to more than 450° C. and the molten filler material is then flowed into the joint portion of the base metal to join the joint portion, and is widely used in industrial fields since it has advantages that it is possible to join different kinds of metals, the joining strength is strong and the sealing property and the corrosion-resistance are excellent.
An end portion of the partition wall 122 which is in contact with the tank 110 is also joined with the tank 110 by the brazing. In this case, a joint area where the partition wall 122 and the tank 110 are in contact with each other is small. Therefore, the joining force is weak and the joining process is difficult, which leads to generation of many defects.
Also, since it is impossible to check the joint portion where the partition wall 122 and the tank 110 are in contact with each other from the outside, it is difficult to check the generation of the defect. Further, although it is possible to check the generation of the defect, it is impossible to find the exact position where the defect is generated.
If perfect sealing is not ensured between the partition wall 122 and the tank 110 as described in above, there are problems that the heat exchange medium does not flow through the given passage but flow abnormally, and the abnormally flowing heat exchange medium obstructs the normal flow of the heat exchange medium and causes a lowering in a heat exchange performance of the heat exchanger.